Active material elements such as shape memory alloy (SMA) wires are used in various devices, such as actuators and smart devices to cause displacements of structural members of the devices by activation of the active elements. This may be done, for example, by passing current through SMA wire, thereby causing it to heat, resulting in contraction of the wire and the application of force to the members it is attached to.
However, when an SMA wire is heated, normally all portions of the wire contract, or attempt to contract, including those portions that are directly attached to a structural member. Such repeated deformation or contraction in the portion(s) of the wire attached to members can result in failure of the device. One failure mode is failure by fatigue due to uneven stress distribution when contraction occurs along a curve. Another failure mode is slide-through of wire at the attachment point leading to pull-out.